The present invention relates to a restriction for conserving air in pneumatic systems and, more particularly, to an elongated restriction having an air conserving flow versus pressure characteristic resulting in reduced air consumption in pneumatic systems.
Pneumatic control systems as opposed to electric control systems are used to control the air conditioning of many buildings today because pneumatic control systems have historically been less expensive to install while at the same time providing adequate air conditioning control. Pneumatic control systems must necessarily require a source of compressed, clean and dry air. This source normally takes the form of a compressor for supplying air to the various sensors and control apparatus located throughout the building.
The sensors and many of these other control apparatus in the building normally take the form of bleed type devices which allow air to leak through the sensor to atmosphere, the amount of air leaking to atmosphere being regulated by the distance between a flapper and a nozzle. The amount of air leaking through the nozzle then governs the pressure in the line leading from the nozzle and it is this varying pressure as the bleed type sensor responds to varying conditions which provides the control pressure for the control system which regulates the controlled conditions.
If very many of these bleed type sensors are used throughout the building, air consumption can become quite large. Therefore, a large compressor is needed in order to supply the necessary amount of air required by the sensors.
Prior art pneumatic control systems have relied extensively upon flat plate restrictions to provide the necessary pressure drops in the control system. These restrictions resulted in convex flow versus pressure characteristics. Such restrictions allowed substantial amounts of air consumption. By reconfiguring the restriction, air consumption in pneumatic control systems can be materially reduced.